Assignment 5: Graph Analysis System

Problem Description

A company manages a network of buildings connected by communication links. The network can be represented as a weighted graph.

Your program must perform three tasks:

1. Traverse the entire graph using BFS and DFS, even if the graph is disconnected.
2. Compute the shortest path from building 0 to all other buildings using Bellman-Ford algorithm (the graph may contain negative edges).
3. Construct a Minimum Spanning Tree (MST) and output the list of edges included in the MST.

If the graph is not connected, the MST cannot be formed.

Input Format

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N M
u1 v1 w1
u2 v2 w2
...
uM vM wM

Where:

• N — number of vertices (0 → N-1)
• M — number of edges
• ui vi wi — undirected edge between ui and vi with weight wi

Constraints

• 1 ≤ N ≤ 1000
• 0 ≤ M ≤ 10000
• -1000 ≤ wi ≤ 1000

Output Format

The program must print three sections.

1. BFS Traversal

Traverse the entire graph using BFS. If the graph has multiple components, continue BFS from the smallest unvisited vertex.

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BFS: v1 v2 v3 ...

1. DFS Traversal

Traverse the entire graph using DFS. When multiple neighbors exist, visit vertices in ascending order.

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DFS: v1 v2 v3 ...

1. Shortest Paths (Bellman-Ford)

Compute the shortest path from vertex 0 to all vertices.

If a vertex is unreachable, print INF.

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ShortestPath: d0 d1 d2 ... d(N-1)

If a negative cycle exists, print:

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NEGATIVE CYCLE

1. Minimum Spanning Tree

If the graph is connected:

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MST Edges:
u1 v1
u2 v2
...
Total Cost: X

If the graph is disconnected:

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MST: IMPOSSIBLE

Edges can be printed in any order.

Example

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Input 1
6 7
0 1 4
0 2 3
1 2 -2
1 3 5
2 3 2
3 4 7
4 5 1

Output 1

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BFS: 0 1 2 3 4 5
DFS: 0 1 2 3 4 5
ShortestPath: 0 1 3 5 12 13
MST Edges:
1 2
0 2
2 3
4 5
3 4
Total Cost: 11

Additional Example (Disconnected Graph)

Input 2

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5 2
0 1 3
3 4 2

Output

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BFS: 0 1 2 3 4
DFS: 0 1 2 3 4
ShortestPath: 0 3 INF INF INF
MST: IMPOSSIBLE

Assignment 6: Smart Transportation Network Analyzer

Problem Description

A smart city manages its transportation network using a graph system.

Each intersection is represented as a vertex, and each road is an edge.

Roads may be:

• bidirectional (two-way)
• one-way

Each road has a travel cost, which may be negative due to toll discounts.

Your task is to build a network analyzer that processes several types of queries about the transportation network.

Input Format

Input consists of multiple commands.

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GRAPH N M
EDGE u v w type
EDGE u v w type
...
QUERY command parameters
QUERY command parameters
...
END

1. GRAPH

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GRAPH N M

• N — number of intersections (0 -> N-1)
• M — number of roads

2. EDGE

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EDGE u v w type

Where:

• u, v = intersections
• w = travel cost
• type:
  • B -> bidirectional
  • O -> one-way (u → v)

Example

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EDGE 0 1 4 B
EDGE 1 3 5 O

3. Query Types

The system must support the following queries.

Case 1 — Network Exploration

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QUERY EXPLORE S

Starting from intersection S, perform:

• BFS traversal
• DFS traversal

Vertices must be visited in ascending order.

Output:

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BFS: ...
DFS: ...

Case 2 — Shortest Routes

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QUERY SHORTEST S

Compute shortest paths from vertex S.

Rules:

• Graph may contain negative edges
• Must use Bellman-Ford

If a negative cycle is reachable from S:

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NEGATIVE CYCLE

Otherwise:

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DIST: d0 d1 d2 ... d(N-1)

Use INF if unreachable.

Case 3 — Build Minimum Network

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QUERY MST

Construct a minimum spanning tree using only bidirectional roads.

Output:

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MST COST X
EDGES k
u1 v1
u2 v2
...

If impossible:

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MST IMPOSSIBLE

Case 4 — Critical Intersections

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QUERY CRITICAL

Find all articulation points in the graph.

Output:

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CRITICAL: v1 v2 v3 ...

If none:

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CRITICAL: NONE

Example

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GRAPH 6 7
EDGE 0 1 4 B
EDGE 0 2 3 B
EDGE 1 2 -2 B
EDGE 1 3 5 O
EDGE 2 3 2 B
EDGE 3 4 7 B
EDGE 4 5 1 B
QUERY EXPLORE 0
QUERY SHORTEST 0
QUERY MST
QUERY CRITICAL
END

Output

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11
BFS: 0 1 2 3 4 5
DFS: 0 1 2 3 4 5
DIST: 0 1 3 5 12 13
MST COST 11
EDGES 5
1 2
0 2
2 3
4 5
3 4
CRITICAL: 3 4